Photographic cameras with motorized film drives are known that will advance newly loaded film to the frame 1 position. High end cameras utilize microprocessor controls that will sense the presence of a cartridge and upon closing of the camera back will initiate the motor drive to advance the film to the first frame position whereupon the motor drive will be terminated. However, the use of microprocessor controls is an expensive proposition and is not suitable for low cost cameras. Low cost motorized cameras are also known that will advance film to the first frame position. These cameras, however, generally require that, after the film cartridge is inserted and the camera back is closed, the motor be activated by pressing the shutter release button.
An example of a prior art film advance motor control circuit of the type just mentioned is shown in FIG. 1. In this control circuit, a timer circuit 10 includes an RC time constant circuit comprising capacitor 12 and resistor 14 coupled between ground and the base of transistor T1. A frame advance timer reset switch S1, ganged with flash initiation switch S6, is moved from contact A to contact B by actuation of the camera shutter release button (not shown) to discharge capacitor 12 for resetting of the timing circuit each time a picture is taken. The emitter of transistor T1 is coupled through film meter sensor switch S2, power on switch S5 and motor wind/rewind switch S7b to the positive terminal of battery 20. The collector of transistor T1 is coupled through resistor divider network 16, 18 to ground. The common terminal 17 of the resistor divider network is coupled to the base of motor drive switching transistor T2. Film drive motor M is coupled between the positive terminal of battery 20 and ground via selectable contacts of wind/rewind switch S7a, S7b, door sensor securement sensor switch S3 and film present sensor switch S4. Door sensor securement sensor switch S3 is closed when the camera back is closed in a light tight position. Switch S4 is closed in response to a sensor at the film gate which senses the presence or absence of film in the film gate. Film meter switch S2 is normally set to contact A which is the motor brake position. It is mechanically engaged with the camera's shutter release button (not shown) such that when the shutter button is released at the end the picture taking cycle, the switch moves to position B to provide power to the motor drive circuit including the timing circuit 10 and motor drive switch transistor T2. Power switch S5 includes a momentary RESET contact which resets a timing circuit in the flash charger portion of flash circuit 22 to begin flash charging as the power switch S5 is moved to the ON contact position. In operation, when film is loaded into the camera and the camera back (door) is secured in the closed position, switches S3 and S4 are closed to complete the circuit to film advance motor M. The motor is not actuated, however, since meter switch S2 is set to the brake contact A and no power is applied to the motor drive timing circuit. To initialize the film to the initial exposure position, usually two or three frames from the beginning of the film strip, it is necessary to actuate the shutter release button for the number of times needed to advance the film the requisite number of frames. When the shutter release button is pressed, timing reset switch S1 is moved to contact B to discharge capacitor 12 thereby resetting the RC timing circuit 12, 14 When the shutter release button is released by the operator, Switch S1 reverts to contact A applying a ground potential to the base of transistor T1 and meter switch S2 moves to contact B applying a positive battery voltage to the emitter of transistor T1 thereby biasing the transistor into conduction. The resultant positive potential at terminal 17 biases motor drive switching transistor into conduction thereby turning motor M on with the switches S7a, S7b set in the motor wind (film advance) direction. When the metering mechanism in the camera senses that the film has moved a distance of one frame, meter switch S2 returns to the motor brake contact A stopping the motor and film advance. If for any reason, the film does not advance, the meter mechanism does not operate to reset the meter switch S2 and the motor continues to run until the charging of timing circuit capacitor 12 causes the base emitter bias of transistor T1 to decrease to the point at which transistor T1 stops conduction. This, in turn, opens motor drive switching transistor T2, thereby stopping the motor M.
The problem with a camera that operates in this manner for film initialization is that, if a consumer loads film in the camera but for some reason the film is not transported to the take-up reel and is not advanced with each press of the shutter release, the motor nonetheless operates in a somewhat normal sounding manner and the camera user thinks that images are being captured but, in fact, they are not. An additional problem is that camera users do not always remember to actuate the shutter release button to advance the film to frame 1 before exposing their first image but rather start taking pictures as soon as film has been loaded. The result is that they may lose several images which they think have been captured. There is a need, therefore, for a low cost film initialization arrangement that will automatically advance the film to the first frame position when a camera back is closed and/or locked without requiring further action by the consumer such as actuating the shutter release button.